PITTSBURGH (AP) - Pittsburgh Steelers chairman and co-owner Dan Rooney is stepping down as the U.S. ambassador to Ireland, a post he assumed after backing President Barack Obama's presidential campaign despite being a lifelong Republican.

The embassy in Dublin says the 80-year-old Rooney resigned Friday and returned to the United States. Press officer John Murphy says Rooney met with Irish Prime Minister Enda Kenny and President Michael Higgins during a final round of engagements this week.

Rooney, the grandson of an Irish immigrant, supported Obama in the 2008 Democratic primary and then campaigned for him.

In an op-ed published Friday in The Irish Times and the Pittsburgh Post-Gazette, Rooney says the relationship between the U.S. and Ireland is as strong as ever. He says the countries' common heritage and values creates a "shared kinship."